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Testing Machines.

the pull is exerted by turning a screw directly or by gear, but in
large machines hydraulic or other power is employed, while the
load is always measured by a smaller weight attached to a lever
or system .of levers, in steelyard fashion. (See pp. 834 and 1065.)

Cement Testing Machine.—Michele's machine will illus-
trate the above details, the load being applied by worm gear at B
to the specimen H} a cement briquette, and the pull measured by
the weight and lever c, or Danish steelyard. The arm D varies

very little, but the arm E increases to the maximum F, or some
shorter distance, during the experiment; the stress therefore varies
as this arm and the pointer is left at its furthest position after
rupture, while the weight returns about half an inch. The scale
is graduated to represent the full load upon H.

Horizontal and vertical testing machines are so named from
the direction of the pull, and each has its particular advantage;
the former Is represented by

The Werder Machine, extensively adopted in Germany,
and shewn in Fig. 329. c is the specimen to be tested, and B an
adjustable washer between shackle and crosshead A, to allow for
length of c. Ram D moves to the right by water pressure from
hand pumps, and the pull is given through the bolts E^ for
tension at c, or compression at G. Trie load is measured by the